Background: Patellofemoral pain syndrome is a prevalent condition in
young people. While it is widely believed that abnormal patellar tracking
plays a role in the development of patellofemoral pain syndrome, this link has
not been established. The purpose of this cross-sectional case-control study
was to test the hypothesis that patterns of patellar spin, tilt, and lateral
translation make it possible to distinguish individuals with patellofemoral
pain syndrome and clinical evidence of patellar malalignment from those with
patellofemoral pain syndrome and no clinical evidence of malalignment and from
individuals with no knee problems.
Methods: Three-dimensional patellofemoral joint kinematics in one
knee of each of sixty volunteers (twenty in each group described above) were
assessed with use of a new, validated magnetic resonance imaging-based method.
Static low-resolution scans of the loaded knee were acquired at five different
angles of knee flexion (ranging between —4° and 60°).
High-resolution geometric models of the patella, femur, and tibia and
associated coordinate axes were registered to the bone positions on the
low-resolution scans to determine the patellar motion as a function of knee
flexion angle. Hierarchical modeling was used to identify group differences in
patterns of patellar spin, tilt, and lateral translation.
Results: No differences in the overall pattern of patellar motion
were observed among groups (p > 0.08 for all global maximum likelihood
ratio tests). Features of patellar spin and tilt patterns varied greatly
between subjects across all three groups, and no significant group differences
were detected. At 19° of knee flexion, the patellae in the group with
patellofemoral pain and clinical evidence of malalignment were positioned an
average of 2.25 mm more laterally than the patellae in the control group, and
this difference was marginally significant (p = 0.049). Other features of the
pattern of lateral translation did not differ, and large overlaps in values
were observed across all groups.
Conclusions: It cannot be determined from our cross-sectional study
whether the more lateral position of the patella in the group with clinical
evidence of malalignment preceded or followed the onset of symptoms. It is
clear from the data that an individual with patellofemoral pain syndrome
cannot be distinguished from a control subject by examining patterns of spin,
tilt, or lateral translation of the patella, even when clinical evidence of
mechanical abnormality was observed.
Clinical Relevance: Since most patients with patellofemoral pain
syndrome did not demonstrate abnormalities in patellar tracking during loaded
knee flexion, other causative mechanisms must be explored to develop effective
diagnostic and treatment strategies for this common musculoskeletal